The present invention relates to an ignite or control circuit device for discharge lamps, more particularly, the present invention relates to an electronic ballast circuit for fluorescent lamps.
Electronic ballast circuits for fluorescent lamps usually adopt a series resonant circuit, that is to say, a resonant circuit consisting of a capacitor, the resistances of the filaments and an inductor connected in series is used to produce a high voltage across the ends of the fluorescent lamp to ignite it, and a rectifying circuit, a filtering circuit and a frequency-converting circuit are sequentially connected between the power supply and the series resonant circuit, with an optional anti-interfering circuit provided before the rectifying circuit in some of the electronic ballast circuits. In this kind of electronic ballast circuit, the resistance of the filaments of the fluorescent lamp might reduce the Q factor of the series resonant circuit, which causes the resonance voltage to be insufficient to ignite the fluorescent lamp, and the lamp will be difficult to start; if the lamp is directly ignited with the filaments resistance shorted, the lamp is started without preheating the filaments, and the life of the filaments of the fluorescent lamp will be significantly reduced by this kind of cold cathode starting; moreover, this kind of existing electronic ballast circuit is suitable to a power supply of 200-240 volts, when the voltage of the power supply is 100-120 volts, the resonant voltage thereof cannot meet the requirement for the normal igniting of the fluorescent lamp.
The object of the present invention is to overcome the disadvantages of the above conventional electronic ballast circuits, and to provide an electronic ballast circuit for fluorescent lamps which has high Q factor and high resonance voltage.